A concrete safe room stands ready for a home to be built around it.Superior Walls of East Tennessee in Rock Island, TN.
Thirteen minutes. That’s all the time you have on average to seek shelter after a tornado warning is issued. If you’re at home when the warning comes, staying put will give you the best odds of survival. And those odds will increase substantially if you a have safe place in your home to ride out the storm.
For people living in wood-frame homes without basements, that “safe” place often ends up being an interior room, such as a closet or bathroom, with no windows. But in a powerful tornado or hurricane packing winds of more than 250 miles per hour, even well-constructed frame houses can be lifted right off their foundations, and large debris can turn into airborne missiles. During such extreme conditions, one of the safest places you can be is in a storm shelter, or safe room, constructed of reinforced concrete or concrete block with no windows and a concrete floor or roof system overhead.
That’s why more and more people, especially homeowners living in tornado-prone areas, are building concrete safe rooms in new and existing homes. When constructed according to approved plans, these windowless, heavily reinforced structures can withstand winds exceeding 250 mph and projectiles traveling at 100 mph or greater, protecting occupants from Mother Nature’s worst wrath.
Building a concrete safe room is not an inexpensive proposition, especially if you are adding one to an existing home. But it’s impossible to put a value on a structure that will give you peace of mind and could save your life. Here are a few factors to consider before building a concrete safe room as well as guidelines and resources for safe room construction.WHAT IS A SAFE ROOM?
A safe room is a small, windowless chamber specifically designed and constructed to meet Federal Emergency Management Association guidelines, which are outlined in the publication Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business (FEMA P-320).
These structures are built to provide “near-absolute protection” for the occupants during extreme windstorms by meeting the following criteria:They are adequately anchored to the home’s foundation to resist overturning and uplift.The connections between all parts of the safe room are strong enough to resist failure during high winds.The walls, roof, and door are designed to resist perforation by windborne missiles.The walls of the safe room are completely separate from the structure of the home, so they will remain standing even if portions of the home around it are destroyed.
Safe room walls and roofs can be built using a variety of materials including reinforced concrete, reinforced concrete masonry or combinations of wood frame and steel sheathing or concrete masonry infill. The doors are typically made of high-gauge steel tested to resist high wind forces and perforation by windborne debris. WHAT IS THE COST OF INSTALLING A SAFE ROOM?
Costs for safe room construction vary across the United States. The cost for constructing an 8- by 8-foot safe room that can double as a closet, bathroom, or utility room inside a new home ranges from approximately $6,600 to $8,700 (in 2011 dollars), according to FEMA. A larger 14- by 14-foot safe room runs from about $12,000 to $14,300.
The main factors that influence the cost of a concrete safe room include:The size The location of the safe room within the home The number of exterior home walls used in the construction of the safe roomThe type of door usedThe type of foundation on which the safe room is constructed
The cost of retrofitting an existing home to add a safe room will vary with the size of the home and its construction type. In general, safe room costs for existing homes will be approximately 20% higher than those in new homes. See this safe room cost calculator from HighWindSafeRooms.org for average remodeling costs for 8- by 8-foot and 14- by 14-foot units made of concrete, concrete block and ICFs.
Some communities offer incentives for owners who wish to build a safe room or shelter, including reduced property taxes. You may also be able to obtain FEMA funding to construct a safe room. For project eligibility, contact your State Hazard Mitigation Officer, who can advise you on what information to provide to be considered for funding. Some state and local governments have engaged in grant programs with the federal government to partially subsidize the construction of safe rooms.
Taking Shelter From the Storm: Building a Safe Room Inside Your House, from FEMAWHY BUILD A SAFE ROOM USING CONCRETE?
By far, the biggest danger to people and property during tornadoes and hurricanes is the flying debris carried by the high winds. Any heavy windborne object can become a missile that can easily penetrate building walls.
To duplicate the effects of windborne debris, researchers at Texas Tech University’s Wind Engineering Research Center shot wall sections with 15-pound 2x4 lumber to simulate debris carried in a 250 mph wind. These conditions cover all but the most severe tornadoes. They tested 4x4-foot sections of concrete block, several types of insulating concrete forms, steel studs, and wood studs to rate their performance. The wall sections were finished as they would be in a completed home, with drywall, fiberglass batt insulation, plywood sheathing, and exterior finishes of vinyl siding, clay brick, or stucco. All the concrete wall systems survived the tests with no structural damage. Lightweight steel and wood-stud walls, however, offered little or no resistance to the test missiles. (You can download the complete Texas Tech report in PDF format.)
You can build concrete safe rooms that withstand such impacts using a variety of methods: cast-in-place concrete, concrete blocks, 4- and 6-inch flat ICF walls, and 6-inch waffle grid ICF walls. Basic safe room designs for all these building types can be found in the FEMA publication Taking Shelter From the Storm, which is available for download on the FEMA website.
In addition to extreme wind events, concrete safe rooms can provide protection from other disasters, including earthquakes, fires, and blast forces. See Disaster Resistance Benefits of Concrete, from the Portland Cement Association.CONCRETE STORM SHELTER CONSTRUCTION TYPES
There are a number of ways to construct concrete saferooms. The three most common methods are with ICFs, concrete masonry and conventionally cast concrete.
Basic saferoom design with concrete blocks, traditionally cast concrete, and for 4- and 6-inch flat ICF walls and 6-inch waffle grid ICF walls may be found in the FEMA publicationTaking Shelter From the Storm: Building A Safe Room Inside Your House, which includes construction plans, materials, and construction cost estimates. It's available from FEMA at no charge by calling toll free (800) 480-2520.
For additional information on ICF safe rooms contact Polysteel at (800) 977-3676 or Lite-Form International at (800) 551-3313.Insulated concrete forms (ICFs)
ICFs are basically forms for poured concrete walls that stay in place as a permanent part of the wall assembly. Made of foam insulation or other insulating material, they come in two basic configurations: pre-formed interlocking blocks into which the concrete is poured, and as individual panels with plastic connectors that form cavities into which the concrete is poured. All major ICF systems are engineer-designed, code-accepted, and field-proven.
To further help homebuilders and homeowners build economical safe rooms for new and existing homes, the Portland Cement Association, American Polysteel, and Lite-Form International worked together to develop safe room plans specifically for insulating concrete forms (ICFs).
Up until now, the Federal Emergency Management Agency's (FEMA) guide for safe room construction included plans for conventionally cast concrete safe rooms and reinforced concrete masonry safe rooms. The new plans include details for 4- and 6-inch flat ICF walls and 6-inch waffle grid ICF walls.
Read more about this project here and view project photos.
For more information about ICFs, click hereConcrete masonry
Concrete blocks are another quick, relatively simple method for building a saferoom. Water repellant can now be mixed into the block at the plant, and additional sealer and flashing applied on-site. Foam insulation is used as a moisture repellant, while lightweight metal brackets allow space for wiring and plumbing.
Concrete masonry can be used in new construction, on existing homes, and in stand-alone saferooms.
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